Round Two: 2010 Toyota Prius III vs. 2010 Volkswagen Golf TDI DSG
Diesels versus Hybrids: Golf TDI Quattroporte Takes On the World's Most Notorious Gasoline Scrooge
Since Volkswagen's little oil-burner can trump Honda's latest in hybrid tech, how about we up the ante and compare a quattroporte version with the world's most notorious gasoline scrooge, the hyper-hybrid Prius? At a combined EPA rating of 50 mpg (FYI, 93 Prius owners are currently reporting an average of 48.8 mpg at www.fueleconomy.org), the Prius runs away with the mpg facet of this contest. By contrast, our TDI offers an impressive -- but in this lofty company, comparably feeble -- 34 combined EPA mpg. Recomputed the way it ought to be, as gallons per 100 miles, the Prius requires 2.0 gallons to cover a Benja-mile, the Golf, 2.94, or 47 percent greater consumption per mile. As Queen Victoria was gently (and probably apocryphally) answered while watching the yacht America run away with the Hundred Guinea Cup race in 1851 (today's America's Cup), "Your majesty, there is no second."
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And it gets worse. Just about nobody seems to realize that diesel's longer-chain hydrocarbons silently provide it with about 11 percent more energy per gallon than gasoline (it's heavier by about that too). In other words, when comparing diesel and gasoline engines, a diesel's first 11 percent (or thereabouts) of its 30-40-percent-greater efficiency ought to be discounted simply due to its denser energy content.
Before you speed-type me those flame mails, I've now read about 312 breathless tales from diesel drivers asserting things like they just got 70 mpg (nay, 85 mpg!) on the way back from Aunt Margaret's in Bakersfield. Last year we carefully logged a long-term Jetta TDI for 20,000 real-world miles and it returned... (snarl-roll)...34.8 mpg (rim-shot). Not bad actually: Its EPA combined figure was 33.1 mpg. Perhaps miracles do happen, but on any particular drive you take, a zephyr of a tail breeze, or an imperceptible grade can starkly affect any individual outcome. Of course, it's the good runs that get remembered.
Note that, in the case of both of our Volkswagen TDIs, we're talking about a rather impressive example of a modern diesel engine. Not only does its injection provide multiple, lightening-quick pulses to quiet knock and mitigate emissions, but its turbocharger plays the role of the perfect sidekick. Why, diesels and turbos go together like Al and Tipper-er, well, better than them, even.
How come?
Besides their high mechanical compression ratio (here, 16.5:1) and throttle-free induction (diesels are essentially unrestricted air pumps, the power they produce being simply a question of how much fuel's injected), adding turbo to a diesel recovers a percentage of the exhaust's residual energy without the drastic compression ratio reduction a turbo-gas engine would require. No wonder diesel trucks invariably whistle with spooling turbochargers.
And speaking of diesel trucks, our domestic diesel car fleet might not exist without them. Believe it or not, only two percent of our diesel fuel is consumed by light-duty vehicles in this country, the rest mainly going to the trucking industry. More background: From a typical 42-gallon barrel of oil, you can expect to produce 18-20 gallons of gasoline (from the oil mix's lighter molecules) and 9-10 gallons of diesel fuel (which employs its heavier constituents). Refineries can adjust this ratio, but it takes energy (and cost) to crack those longer-chain molecules or combine the short ones. The ratio's also affected by a particular well's chemical personality, whether it's "heavy" (containing more long molecules), "light" (a greater proportion of short ones), "sweet" (low sulfur), or "sour" (lots of sulfur). As a practical matter, we really don't want all cars to be running on either diesel or gasoline.
Which brings us back to our Prius.
To America's Hollywood-suspicious, global-warming-denying, and otherwise grumpy folk, the Prius is sort of an alien spacecraft descended from the Planet Namby-Pamby sent here to put decent, don't-tread-on-me folks into its zombie trance. Its barracuda profile disturbingly suggests there's "air drag" to even think about. And e-lec-tricity? Fine for keeping the Coors cold and the flat-screen bright. But propelling cars? Hunny-Bun! Where's El Rushbo's speed-dial button?
Frankly, the Prius offers a pretty fat target as it's virtually talentless at entertaining you with the drops of fuel it does burn. Do its low-rolling resistance tires (our car, by the way, was fitted with the smaller offerings) really sacrifice this much pavement feel? Though the Prius provides an undeniable Einsteinian intellectual satisfaction whilst gliding along in 50-mpg bliss -- ooooommm -- apparently some people expect more than this:
Benson Kong on the walkie-talkie: "This is my first time driving a Prius. Is this as fast as it goes?"
Yes, Benson.
Ed: "The Prius is slow (9.7 seconds to 60), but its performance is not uniformly terrible. Those little tires hang on for dear life in corners (without much crying), and I like the brake pedal sensation of all those burned dinosaurs being recouped (cheer-up, IEEE, there's hope for ol' Ed yet)."
Also over the walkie-talkie, I happened to mention that the Golf TDI reminds me of the lighter, smaller (and, to me, more elegant) 3 Series cars BMW used to build. "I know what you mean," Ed replied. "This car's a delight in the twisty sections, it is indeed 3 Series-esque. However it's missing one key element: a lovely exhaust note. Still, the DSG is wonderful, well suited to the TDI in S mode, although it won't always serve up the gears you want, especially when calling for higher-rpm downshifts...frustrating (a consequence of the diesel's low redline, no doubt).
And listen, if you're among those still suffering from manual myopia, still blithely blaspheming double-clutch trannies, I've got some troubling evidence to share. This 97-pound-heavier, four-door DSG-equipped sibling to the manual two-door reached 60 mph three tenths sooner and returns 1-mpg-better highway mileage. Shifts faster too. And you can keep both hands on the wheel in the corners, and...look, need I continue? It's time to move on, troops.
Speaking of which, the view forward appears to be one of gathering clouds for diesels as concerns rise about things like microparticulates, while they're slowly parting on the hybrid horizon. Right now, we're driving a plug-in Prius that's getting astonishing mileage; leveraging the hybrid's existing electrical componentry represents a technologically compelling path forward (if a dubious economic one). The diesel has no obvious place to go from here.
However, in the here and now, both the Prius and Golf TDI are offering terrific mileage, with both are so far out on the thin edge of the bell curve you can just about see through it. So the choice between them comes down to...well, tell you what.
Don your favorite hat and stand in front of a mirror. What's on the front of it? Mine (okay, it's free and I'm balding) says "Motor Trend." If yours says something similar, then we agree that cars are a whole lot more than simple mileage machines; TDI triumphs again.
And if your cap screams with "Stop imported oil!" or "Save the Polar Bear!"(or at least holds down thoughts to that effect), gosh, just pick the car here with the seats and doors and style you like. You won't go wrong.
1ST PLACE:Volkswagen GolfTDI DSG
The TDI wins this round too, but only by a few strokes. The Golf's bigger tires, faster steering, and conventional styling make for an interesting counterpoint to the mileage-is-everything Prius.
2ND PLACE:Toyota PriusIII
Futuristic, intellectually entertaining, and certainly the fuel-economy choice for non-car enthusiasts. The Prius's problem is that ain't us.
